The present invention relates to a slip coupling,                wherein the slip coupling has a pair of coupling elements,        wherein the two coupling elements are rotatable about a common axis of rotation and have a coupling surface that is annularly circumferential around the axis of rotation in each case.        
Such slip couplings are well known—particularly in the railroad industry.
Drives for rail vehicles often comprise a motor which is mounted in a wheel truck (bogie) of the rail vehicle, and a gearbox which is in turn mounted on the driving wheel axle of the rail vehicle and supported on the wheel truck via a torque support arm. Also usually disposed between the motor and the gearbox is a universal (Cardan) coupling which compensates the relative movement between the wheel truck and the driving wheel axle and transmits the drive torque from the motor to the driving wheel axle.
During normal operation, such rail drives produce acceleration torques (possibly in both directions) and deceleration torques (possibly likewise in both directions). This causes the rail vehicle and other rail vehicles coupled to the rail vehicle to be accelerated and decelerated accordingly. These normal torques are occasionally exceeded by very brief, in some cases very greatly increased so-called short-circuit torques which may result from the interaction of a power converter feed and the motor. The rail drive can be designed such that these large short-circuit torques are absorbed by all the supporting parts within the drive unit. Alternatively, the effect of the short-circuit torques has to be limited. To limit the effect, load-reducing elements such as a slip coupling of the type described above are generally provided.
During operation, rail drives may also encounter fault situations in which the design torque of the drive is persistently exceeded for an extended period of time. This is the case, for example, if damage occurs in the motor, as a result of which the rotor of the motor is no longer adequately guided. In individual cases this can cause the rotor to rub or even jam in the stator bore of the motor. In particular, such jamming of the rotor can result in consequential damage which may reach a considerable degree of severity. In order to prevent such damage, it is necessary not only to limit the torque transmitted via the slip coupling, but also to release the slip coupling so that torque transmission (the frictional connection) between motor and driving wheel axle is interrupted.